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PubMed2000

Emendation of the generic diagnosis of Tylocephalum (Cestoda: Lecanicephalidea: Tetragonocephalidae), and description of Tylocephalum brooksi n. sp.

A new species of Tylocephalum is described from the spiral intestine of the cownose ray Rhinoptera bonasus taken off Venezuela. Tylocephalum brooksi n. sp. is the third species described parasitizing this host species, along with T. pingue and T. bonasum. T. brooksi is similar to congeners in the possession of a scolex with a fungiform pars apicalis, craspedote segmentation, circummedullary vitellarium, external seminal vesicle, bilobed ovary, and medioventral uterus. However, this species differs from all previously described species of Tylocephalum in having a collar around the base of the pars apicalis densely covered by large digitiform processes (microtriches?), and an internal seminal vesicle. The internal seminal vesicle is a feature currently used to differentiate Tetragonocephalum from Tylocephalum. Its presence in T. brooksi indicates that it should be considered a specific instead of a generic character. An emended diagnosis of Tylocephalum is proposed excluding this feature, along with distribution of the testes in the preovarian field and circummedullary distribution of vitelline follicles. Species of Tylocephalum and Tetragonocephalum are reviewed on the basis of original descriptions, and 2 distinct morphological groups of species defined. Species of the Tetragonocephalum group possess a combination of an acraspedote strobila, segments much longer than wide, testes limited to the region anterior to the cirrus sac, vitellarium of lateral bands, conspicuously enlarged genital atrium and pore, cirrus sac dorsal to genital atrium, and bisaccate uterus. Species of the Tylocephalum group differ from Tetragonocephalum in possession of a craspedote strobila, segments more quadrangular, testes distributed throughout the preovarian field, inconspicuous genital atrium, uniformly saccate uterus, cirrus sac lateral to genital atrium, and probable circummedullary vitellaria in all species.

Animals↗
PubMed1997

Six species of Acanthobothrium (Eucestoda: Tetraphyllidea) in stingrays (Chondrichthyes: Rajiformes: Myliobatoidei) from Ecuador.

Six species of Acanthobothrium, 4 described as new, are reported in stingrays from southern Ecuador. Acanthobothrium atahualpai n. sp. in Gymnura afuerae most closely resembles Acanthobothrium fogeli and Acanthobothrium parviuncinatum by having bothridial hooks with recurved prongs and short handles. It differs from A. fogeli by having bothridial hooks 163-195 microns vs. 78-114 microns long and averaging 25 vs. 32 testes per pruglottis: it differs from A. parviuncinatum by having bothridial hooks 163-195 microns vs. 87 microns long and averaging 25 vs. 13 testes per proglottis. Acanthobothrium minusculus n. sp. in Urolophus tumbesensis most resembles Acanthobothrium campbelli and Acanthobothrium vargasi by being no more than 3 mm long and having 6-30 testes per proglottis. It can be distinguished from them by having bothridial hooks averaging 86 microns vs. 108-111 microns and 130-133 microns long, and 6-10 vs. 15-23 and 22-29 testes per proglottis, respectively. Acanthobothrium monksi n. sp. in Aetobatus narinari resembles Acanthobothrium tasajerasi from Himantura schmardae by having a prominent genital atrium and a large globose cirrus sac; it differs by averaging 21 vs. 35 testes per proglottis and having bothridial hooks averaging 150 microns vs. 165 microns long. Acanthobothrium obuncus n. sp. in Dasyatis longus resembles a group of species characterized by wider than long to square immature and mature proglottides, bothridia at least partially fused to the scolex at their posterior ends, and asymmetrical ovarian arms with aporal arms extending anteriorly to the vaginal level. It resembles Acanthobothrium americanum by averaging 73 vs. 72 testes per proglottis, but differs by having bothridial hooks averaging 120-131 microns vs. 151 microns long; it resembles Acanthobothrium chilensis by having bothridial hooks averaging 120-131 microns vs. 130 microns long, but differs by averaging 73 vs. 90 testes per proglottis. Acanthobothrium campbelli in Urotrygon chilensis and Acanthobothrium costarricense in Dasyatis longus, previously known in those hosts from the Pacific coast of Costa Rica, are reported from Ecuador for the first time.

Animals↗
PubMedDate not supplied

[The effect of pentagastrin and ornithine-tetragastrin on motor activity of the stomach in skates and scorpion-fish].

Low doses of pentagastrin (50 mug/kg b. w.) have no physiological effect on motor activity of the stomach in the skate Dasyatis pastinaca. Average doses (100-200 mug/kg) stimulate the activity, whereas high ones (300 mug/kg) inhibit the frequency of stomach contractions, slightly increasing their amplitude. Ornithine tetragastrin in a dose 2000 mug/kg does not affect motor activity of the stomach in skates. In the scorpion-fish Scorpaena porcus, ornithine tetragastrin (1000 and 2000 mug/kg) inhibits motor activity of the stomach.

Animals↗
PubMed1982

Electric and magnetic field detection in elasmobranch fishes.

Sharks, skates, and rays receive electrical information about the positions of their prey, the drift of ocean currents, and their magnetic compass headings. At sea, dogfish and blue sharks were observed to execute apparent feeding responses to dipole electric fields designed to mimic prey. In training experiments, stingrays showed the ability to orient relative to uniform electric fields similar to those produced by ocean currents. Voltage gradients of only 5 nanovolts per centimeter would elicit either behavior.

Animals↗
PubMed1998

Aryl hydrocarbon receptor function in early vertebrates: inducibility of cytochrome P450 1A in agnathan and elasmobranch fish.

The mammalian aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that controls the expression of cytochrome P450 1A (CYP1A) genes in response to halogenated aromatic hydrocarbons such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The natural ligand and normal physiologic function of this protein are as yet unknown. One approach to understanding AHR function and significance is to determine the evolutionary history of this receptor and of processes such as CYP1A induction that are controlled by the AHR in mammals. In these studies, AHR function was evaluated in representative cartilaginous fish (little skate, Raja erinacea) and jawless fish (sea lamprey, Petromyzon marinus and Atlantic hagfish, Myxine glutinosa), using CYP1A induction as a model AHR-dependent response. Treatment of skate with beta-naphthoflavone (BNF) caused an 8-fold increase in hepatic ethoxyresorufin O-deethylase (EROD) activity as well as a 37-fold increase in the content of immunodetectable CYP1A protein. Evidence of CYP1A inducibility was also obtained for another cartilaginous fish, the smooth dogfish Mustelus canis. In contrast, hepatic EROD activity was not detected in untreated lamprey nor in lamprey treated with 3,3'4,4'-tetrachlorobiphenyl (TCB), a potent AHR agonist in teleosts. A possible CYP1A homolog was detected in lamprey hepatic microsomes by one of three antibodies to teleost CYP1A, but expression of this protein was not altered by TCB treatment. CYP1A protein and catalytic activity were measurable in hagfish, but neither was induced after treatment with TCB. These results suggest that the AHR-CYP1A signal transduction pathway is highly conserved in gnathostomes, but that there may be fundamental differences in AHR signaling or AHR-CYP1A coupling in agnathan fish. Agnathan fish such as hagfish and lamprey may be interesting model species for examining possible ancestral AHR functions not related to CYP1A regulation.

Animals↗
PubMed1985

Ontogenic studies on the appearance of two classes of immunoglobulin-forming cells in the spleen of the Aleutian skate, Bathyraja aleutica, a cartilaginous fish.

We identified the presence in the Aleutian skate, Bathyraja aleutica, of two classes of immunoglobulins (Ig), a high molecular weight Ig analogous to mammalian IgM and a low molecular weight Ig, similarly to the spiny rasp skate, Raja kenojei, (Kobayashi, K. et al., Mol. Immunol. 1984. 21: 397), using an immunological cross-reaction with the specific antisera to the spiny rasp skate Ig components. The antigenic similarity of the heavy chains of the Ig of the Aleutian skate and those of the spiny rasp skate was less than that between their light chains. Two types of Ig-producing cells, one producing the high molecular weight and the other forming the low molecular weight Ig, were present in the spleen of embryos and adults in the Aleutian skate at a ratio of 5-6:4-5. The number of these Ig-producing cells increased with advancing development of the embryos but was 1/20 to 1/50 of those of adults. Cells, each of which were capable of forming both classes of Ig, were found in the spleen of embryos but not in that of adults. These results suggested that the spleen of the Aleutian skate is the primary lymphoid organ for B lymphocyte differentiation and proliferation, possibly equivalent to the bursa of birds.

Animals↗
PubMed1987

Immunocytochemical analysis of the dopamine system in the forebrain and midbrain of Raja radiata: evidence for a substantia nigra and ventral tegmental area in cartilaginous fish.

The distribution of dopamine-containing cell somata and fibers in the forebrain and midbrain of a cartilaginous fish, Raja radiata, was investigated by means of antibodies directed against dopamine. Many small dopamine immunoreactive neurons are distributed throughout the telencephalon, including the olfactory bulbs. Within the diencephalon and particularly in the hypothalamus, i.e., in the nucleus preopticus, nucleus suprachiasmaticus, the paraventricular organ, lateral hypothalamic area, recessus mamillaris, and nucleus tuberculi posterioris, numerous cell somata stain for dopamine. In the mesencephalon, two distinct cell masses are found, which on the basis of their immunoreactivity for dopamine and their location, may be homologous to the substantia nigra and ventral tegmental area of other vertebrates. Dopamine immunoreactive fibers are found in the glomeruli of the olfactory bulbs, in ventral portions of the telencephalon, where a dense dopaminergic plexus innervates the area superficialis basalis and striatum, and in the diencephalon, where the inferior lobe is the most densely innervated structure. In the mesencephalon, the dopamine immunoreactive fibers are confined predominantly to the periventricular zone and lateral portions of the tectum. We conclude that much of the dopaminergic system in Raja radiata is strikingly similar to that seen in amniotes.

Animals↗
PubMed1989

Brain variation and phylogenetic trends in elasmobranch fishes.

A cladistic analysis utilizing the out-group criterion to establish the phylogenetic polarity of neural features among living chondrichthyans leads to the conclusion that the earliest chondrichthyans possessed relatively small brains. Relative brain size appears to have increased independently in some myliobatiforms and in the common ancestor of heterodontid and galeomorph sharks. Furthermore, the brains of the earliest chondrichthyans must have exhibited a wide rhomboid fossa of the medulla, an unfoliated cerebellar corpus divided into anterior and posterior lobes, a bilobed and laminated optic tectum with the majority of the cell bodies located periventricularly, a moderately developed midbrain octavolateralis complex, and a telencephalon consisting of sessile olfactory bulbs and paired cerebral hemispheres with extensive lateral ventricles and thin walls. The corpus of the cerebellum has increased dramatically in size and has become complexly foliated independently in some batoids and galeomorph sharks. Similarly, the majority of tectal neurons have migrated away from a periventricular zone in all living elasmobranchs resulting in two distinctly derived patterns, compared to that in holocephalimorphs, but the polarity of these patterns among elasmobranchs is uncertain. The midbrain octavolateralis complex is uniquely derived in all living batoids, but two patterns appear to occur in other chondrichthyans, and, again, their polarity is uncertain. Different portions of the telencephalic roof appear to have hypertrophied in holocephalimorphs, in some batoids, and in some galeomorphs. An examination of pertinent details of chondrichthyan general biology reveals that the biological significance of most chondrichthyan neural trends is unknown.

Animals↗
PubMed1991

Swimming in a sub-adult monogenean of the genus Entobdella.

Swimming in a sub-adult monogenean parasite is reported for the first time. When detached from the substrate, a specimen of an undescribed species of Entobdella from the ventral skin surface of the cow-tailed ray, Dasyatis sephen, was found to propel itself vigorously through the water, head-first, by rapid dorso-ventral body undulations travelling in an antero-posterior direction. These waves pass in the opposite direction to the slower breathing (?) undulations exhibited by the attached parasite. Benedeniella macrocolpa from another elasmobranch host and benedeniines from teleost fishes merely made uncoordinated wriggling movements when detached from the substrate. The possible function of swimming in monogeneans is discussed.

Animals↗
PubMed2005

Envenomations.

Numerous types of envenomations may be encountered by health care workers depending on where in North America they work. Clinicians should be familiar with the animals in their region that may lead to envenomation.A rational approach with use of poison center or medical toxicology consultation services ensures that cases are managed appropriately.

Animals↗
PubMed2000

Heliocotyle ewingi sp. n. (Monogenea: Monocotylidae) from the gills of Myliobatis australis (Myliobatididae) from Tasmania, Australia.

Heliocotyle ewingi sp. n. (Monogenea: Monocotylidae) is described from the gills of Myliobatis australis Macleay, 1881 (Myliobatididae) collected from Norfolk Bay near Hobart, Tasmania, Australia. Heliocotyle ewingi can be distinguished readily from the only other species in the genus, Heliocotyle kartasi Neifar, Euzet et Ben Hassine, 1999, by the presence of a single pseudoseptum on each of the peripheral loculi except the posteriormost, eyespots and by the morphology of the male copulatory organ which is a short, straight sclerotised tube which lacks a sclerotised accessory piece. The generic diagnosis is revised to accommodate the new species and the anterior glands are discussed.

Animals↗
PubMed2006

Description of a new ascarid species in elasmobranchs from Taiwan Strait.

A new ascarid of elasmobranchs, Terranova amoyensis sp. n., is described from the intestine of the red stringray, Dasyatis akajei (Müller and Henle), from Taiwan Strait. This is the second report from this genus with a gubernaculum in fish. The new species differs from its congeners mainly in the following combination of characters: the 3 lips are unequal in size and different in shape, i.e., the subventral lips are asymmetric bilaterally and larger than the dorsal lip; the latter lip is bilaterally symmetrical. The ventriculus is spherical, and the cecum is short relative to the esophagus. Spicules are unequal in size, 1.48 mm long for the right spicule and 1.34 mm for the left spicule, or 4.3 and 3.9% of body length, respectively. Nineteen pairs of caudal sessile papillae (excluding phasmids) are present, of which 13 pairs are precloacal; pairs 14 and 15 lie close together on either side of the cloaca, composing ad-cloacal papillae (the pair near the tail end are twins). The remaining 4 pairs of postcloacal papillae form a group near the tail tip (pair 18 also twins and near the phasmids). The gubernaculum is I-shaped. The excretory pore is located on top of a coniform prominence whose location is just behind or between the bases of the 2 subventral lips. The vulva is prominent at one-third of the anterior part of the body; the distance from the vulva opening to the anterior body end is 17.4 mm (13.61-21.41), 26.8% (25.14-28.93%) of the body length.

Animals↗
PubMed2006

Nitric oxide production by nurse shark (Ginglymostoma cirratum) and clearnose skate (Raja eglanteria) peripheral blood leucocytes.

Reactive nitrogen intermediates, such as nitric oxide (NO), are important immunomodulators in vertebrate immune systems, but have yet to be identified as mediators of host defence in any member of class Chondrichthyes, the cartilaginous fishes. In the present study, production of NO by nurse shark (Ginglymostoma cirratum) peripheral blood leucocytes (PBL) stimulated with bacterial cell wall lipopolysaccharide (LPS) was investigated. PBL were cultured for 24 to 96 h following stimulation with LPS at concentrations ranging from 0 to 25 microg ml(-1), in both serum-supplemented and serum-free culture conditions. Production of NO was measured indirectly using the Griess reaction, with maximal NO production occurring after 72 h using 10% FBS and 10 microg LPS ml(-1). Application of these culture conditions to PBL from another cartilaginous fish (clearnose skate, Raja eglanteria) resulted in a similar NO response. Addition of a specific inhibitor of inducible nitric oxide synthase (iNOS), L-N(6)-(1-iminoethyl)lysine (L-NIL), resulted in a significant decrease in the production of NO by PBL from both species.

Analysis of Variance↗
PubMed1989

Flagellar cells and ciliary cells in the renal tubule of elasmobranchs.

Flagella or cilia are present on most epithelial cells in the renal tubule of elasmobranch fishes (little skate, spiny dogfish, smooth dogfish, Atlantic sharpnose, scalloped hammerhead, cow-nosed ray). Flagellar cells, those with numerous flagella ordered in one, two, or more rows on the luminal surface, are shown here for the first time in a vertebrate. The flagellar cells are intercalated among other epithelial cells, each bearing a single cilium, from Bowman's capsule to the third subdivision of the intermediate segment of the nephron. The flagella form undulated ribbons up to 55 microns long. In every ribbon the axis of the central pair of microtubules in the axoneme is oriented parallel to the long axis of the flagellar row. This suggests a beat perpendicular to these two axes. The arrangement of the flagella in ribbons most likely promotes movement of glomerular filtrate down the renal tubule. Cells bearing numerous cilia occur in the large collecting ducts of spiny dogfish but without apparent preferential orientation of the cilia.

Animals↗
PubMed1985

J-chain-like component in 18-S immunoglobulin of the skate Raja kenojei, a cartilaginous fish.

A J-chain was found in the IgM, an 18-S pentameric immunoglobulin, of the skate, Raja kenojei, a cartilaginous fish, by means of gel filtration-column chromatography of reduced and radioalkylated immunoglobulin, followed by alkaline-urea polyacrylamide gel electrophoresis. The J-chain showed an electrophoretic mobility equivalent to that of the light chain, and much slower than that of the J-chain in human IgM. Its electrophoretic banding patterns, however, were different from those of the light chain. Its mol. wt of 17,500 was close to that of mammalian J-chain. The J-chain was not found in another immunoglobulin of the skate, a 9-S dimer held by a noncovalent force. No immunological cross-reactivity was observed between the skate J-chain and human and chicken J-chains. In view of these findings, it was concluded that the J-chain in the skate IgM is both electrophoretically and antigenically considerably different from the J-chain in mammalian IgM.

Animals↗